<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>按钮</title>
</head>

    <style>
        button
        {
            position:absolute;
        }

        button#b1
        {
            top:20%;left:25%;
            nav-index:1;
            nav-right:#b2; nav-left:#b4;
            nav-down:#b2; nav-up:#b4;
        }

        button#b2
        {
            top:40%;left:50%;
            nav-index:2;
            nav-right:#b3; nav-left:#b1;
            nav-down:#b3; nav-up:#b1;
        }

        button#b3
        {
            top:70%;left:25%;
            nav-index:3;
            nav-right:#b4; nav-left:#b2;
            nav-down:#b4; nav-up:#b2;
        }

        button#b4
        {
            top:40%;left:0%;
            nav-index:4;
            nav-right:#b1; nav-left:#b3;
            nav-down:#b1; nav-up:#b3;
        }
    </style>
</head>
<body>

<button id="b1">Button 1</button>
<button id="b2">Button 2</button>
<button id="b3">Button 3</button>
<button id="b4">Button 4</button>

<p><b>注释：</b>目前只有 Opera 支持 nav-* 属性。当您使用方向键导航时，请同时按下 Shift 键。</p>


</body>
</html>